The present invention relates to a swash plate type compressor in which a piston is reciprocated by a swash plate in the manner known in the art.
Such a swash plate type compressor is often included in an air conditioner for an automobile or a vehicle. The swash plate type compressor generally comprises a cylinder block defining a cylinder bore, a piston inserted in the cylinder bore, a swash plate rotatably driven by a driving mechanism known in the art, and a shoe mechanism slidably interposed between the swash plate and the piston. The swash plate is fixed to a driving shaft rotated by a driving source such as an engine mounted on the automobile. The shoe mechanism is for converting a rotating motion of the swash plate to a reciprocating motion of the piston in the manner known in the art. When the swash plate reciprocates the piston, a gaseous fluid is compressed in the cylinder. In case of using the swash plate type compressor in the air conditioner, a refrigerant gas is used as the gaseous fluid and circulates through a refrigerating cycle included in the air conditioner.
If wear or abrasion occurs in a sliding portion between the swash plate and each of the piston and the shoe mechanism, the compressor has reliability which may be significantly reduced. Accordingly, constant lubrication should be ensured for the sliding portion.
In the swash plate type compressor of this kind, lubricating oil is stored in a crankcase, containing the swash plate, in order to lubricate the sliding portion and others. When the swash plate is rotated, the lubricating oil is splashed and attached to the sliding portion by reactions of the swash plate and others.
However, it is hard to obtain the effect of lubrication when the amount of the lubricating oil is small in the crankcase. This is because the lubrication of the sliding portion is conducted without control of the lubricating oil.
As an example for solving such a problem, a compressor is disclosed in Japanese Patent Unexamined Publication No. 5-44641 in which a passage is formed in a piston to conduct a lubricating oil to a sliding portion. However, positive lubrication is not possible because the passage has an oil inlet and an oil outlet which are similar to each other in pressure.
In the manner known in the art, the lubricating oil has a part which leaks from the crankcase and circulates together with the refrigerant gas through the refrigerating cycle. That is, the refrigerant gas in the refrigerating cycle includes the lubricating oil. When the piston is reciprocated, the refrigerant gas has a part which passes as a blowby gas towards the crankcase through a sealed gap left around the piston. In this event, the blowby gas includes the lubricating oil in addition to the refrigerant gas.